1. Field of the Invention
The present invention relates to a method and apparatus for indicating the number of blanks to be introduced into a manufacturing apparatus to be formed into products classified into ranks according to their properties, so that the number of blanks does not exceed a maximum production value previously set for each of the product ranks. The invention also relates to a manufacturing system for manufacturing products using the method.
2. Description of the Related Art
In general, even when a plurality of blanks is simultaneously processed under the same conditions in the same lot using a manufacturing apparatus, products having different properties are manufactured at a ratio characteristic of the manufacturing apparatus. For example, if 100 blanks, introduced into the manufacturing apparatus and processed under the same conditions, are classified into four ranks, Ranks 1 through 4, according to their properties, and if it is assumed that ten Rank-1 products, thirty Rank-2 products, twenty Rank-3 products, and forty Rank-4 products are manufactured, the ratio at which each of the products according to Ranks 1 through 4 is manufactured (hereinafter referred to as output ratio) is 10%, 30%, 20%, and 40%, respectively.
In consideration of the output ratio conventionally based on the ranks of the products, the number of blanks to be processed by a manufacturing apparatus has been computed using a method such as that shown in FIG. 7. Here, the numbers of products ordered for Ranks 1 through 4 are assumed to be a, b, c, and d respectively, and the output ratio for Ranks 1 through 4 are assumed to be A %, B %, C %, and D % respectively. First, in Step S1 of the method, the number of blanks necessary to manufacture each of the products for Ranks 1 through 4, N1 through N4, is determined. The number of blanks to be introduced is obtained by dividing the number of products ordered according to the product ranks by their respective output ratios. That is, for Rank-1 products, this number is obtained by calculating N1=100 a/A. Next, in Step S2, the largest value, N, among N1 through N4 computed according to the ranks is obtained. In Step S3, the largest value, N, is output as the number of blanks to be introduced to satisfy the amount of orders made for all of the product ranks.
In this way, hitherto, the number of blanks for accomplishing the production plan has been calculated according to rank, the largest value among the computed quantities being the final number of blanks to be introduced. As a result, there has been a problem in that an excess of some of the product ranks was produced. When the number of products produced exceeds, for example, a value which is the sum of the number of products ordered and the number of products which can be stocked, it is necessary to dispose of the excess products.